Phase-change ink printing systems include various imaging devices that offer many advantages over other types of document reproduction technologies, such as laser and aqueous inkjet approaches. These advantages often include higher document throughput (i.e., the number of documents reproduced over a unit of time), fewer mechanical components needed in the actual image transfer process, fewer consumables to replace, and sharper images.
A typical solid ink or phase-change ink imaging device includes an ink loader, which receives and stages solid ink for delivery to a melting device. The ink supply can be replenished by a user inserting more solid ink into the loader. The loader has separate loader channels, each of which supplies a different color of ink to a melting device. For example, four loader channels are provided in an imaging device that uses cyan, magenta, yellow, and black (CMYK) ink to form ink image images. Solid ink is supplied in a variety of forms that include blocks, sticks, pellets, and pastilles, for example.
Solid ink imaging devices melt the solid ink to a liquid phase for imaging operations. In a typical embodiment, a melting device heats the solid ink to a temperature at which the solid ink enters a liquid phase. The one or more printheads in an imaging device receive the liquid ink and eject liquid drops of the ink through a plurality of inkjets onto an image receiving member, such as paper, or an indirect receiver, such as a rotating drum or endless belt. Many printer embodiments maintain a supply of liquefied ink in an ink reservoir that is fluidly coupled to one or more printheads for printing onto the image receiving member.
In some printers, gravity urges ink in the reservoir to flow to the printheads. In other printers, a pumping system applies pressure to liquid ink in the reservoir to urge the ink to the printheads. Continuous feed printers form images on an elongated media web that moves through the printer at a high speed for high-volume production. These continuous feed printers often consume ink at a high rate and require a pressurized ink reservoir to maintain a uniform supply of ink to the printheads. In one type of continuous printer, two separate delivery reservoirs supply ink to a common set of printheads using an alternating operating technique. In the alternating operating technique, one of the two delivery reservoirs is connected to a low pressure reservoir to enable ink to flow from the low pressure reservoir to the connected delivery high pressure reservoir side while the other delivery reservoir is disconnected from the low-pressure reservoir and the high pressure reservoir side is pressurized to deliver ink to the printheads. When the level of ink in the pressurized delivery reservoir drops below a predetermined fluid level, the pressurized delivery reservoir is disconnected from the pressure source, a double-ended seal piston is toggled to enable ink to flow from the low pressure reservoir. The other ink delivery reservoir is disconnected from the low-pressure reservoir and pressurized to deliver ink to the printheads. In one implementation of the alternating process, each of the ink delivery reservoirs includes a piston. The two pistons are mechanically linked so that one piston seals one ink delivery reservoir from the low-pressure reservoir, while the other piston simultaneously opens the other ink delivery reservoir to receive ink from the low-pressure reservoir. The alternating arrangement of the two delivery ink reservoirs enables a substantially continuous supply of ink to the printheads during printing operations.
One challenge facing a pressurized reservoir system involves the depressurization of the ink delivery reservoirs. The challenge arises from the pressurization of an air pocket positioned over the ink held in the ink delivery reservoir. When the level of ink in the pressurized reservoir drops below the predetermined threshold and the ink delivery reservoir is placed in fluid communication with the low-pressure reservoir, the pressurized air exits the delivery reservoir and enters the low-pressure reservoir through the valve seat opening. This pressurized air exits through the valve seat opening to cause ink held in the low-pressure reservoir to splatter and aerosol some of the ink in the low-pressure reservoir. Ink droplets resulting from the splatter may escape the low-pressure reservoir through openings in the low-pressure ink reservoir. Some of the escaped ink may contaminate the air supply vents and cause premature failure by blocking the air flow in the vent line. Consequently, improvements to the operation of the pressurized ink delivery system to prevent ink contamination would be beneficial.